Blockchain data

ABSTRACT

A coupon-minter is configured to perform operations including: generating a coupon comprising encrypted discount information, wherein the encrypted discount information is encrypted with a discount key; generating, for the coupon, a hashlock from a preimage; introducing the coupon to a blockchain in association with the hashlock, wherein the blockchain is configured to permit claiming of the generated coupon only upon receiving access to the preimage used to generate the hashlock. A store-manager configured to perform operations including: claiming, using the preimage, the coupon in the blockchain; encrypting the discount key with a clearing-house public key; updating the coupon with the encrypted discount key. A clearing-house-manager configured to perform operations comprising: detecting the store-manager&#39;s claiming of the coupon; decrypting the encrypted discount key with a clearing-house private key to re-generate the discount key; and decrypting the encrypted discount information with the preimage.

The present document relates to computer technology for tracking data ina blockchain.

BACKGROUND

A blockchain is a distributed datastore that maintains acontinuously-growing list of ordered records called blocks. By designblockchains are inherently resistant to modification of the data—oncerecorded, the data in a block cannot be altered retroactively.Blockchains include an open, distributed ledger that can recordtransactions between two parties efficiently and in a verifiable andpermanent way.

SUMMARY

In one aspect, a system includes a coupon-minter configured to performoperations including: generating a coupon comprising encrypted discountinformation, wherein the encrypted discount information is encryptedwith a discount key; generating, for the coupon, a hashlock from apreimage; introducing the coupon to a blockchain in association with thehashlock, wherein the blockchain is configured to permit claiming of thegenerated coupon only upon receiving access to the preimage used togenerate the hashlock. The system includes a store-manager configured toperform operations including: claiming, using the preimage, the couponin the blockchain; encrypting the discount key with a clearing-housepublic key; updating the coupon with the encrypted discount key. Thesystem further includes a clearing-house-manager configured to performoperations comprising: detecting the store-manager's claiming of thecoupon; decrypting the encrypted discount key with a clearing-houseprivate key to re-generate the discount key; and decrypting theencrypted discount information with the preimage. Similar methods andcomputer readable mediums containing operations may also be used.

Implementations can include any, all, or none of the following features.The coupon-minter, the store-manager, and the clearing-house-manager areeach further configured to authenticate records of claims submitted tothe blockchain. The coupon-minter is further configured to: receive anorder to generate a plurality of coupons, each having the discountinformation; and generate a plurality of coupons, including the coupon,each of the plurality of coupons having the discount information andeach of the plurality of coupons having a different preimage. Tointroduce the coupon to the blockchain in association with the hashlock,the coupon-minter is configured to introduce the coupon to theblockchain in a wallet assigned to the coupon-minter. To claim thecoupon in the blockchain, the store-manager is configured to move thecoupon from the wallet assigned to the coupon-minter to a walletassigned to the store-manager. To observe the store-manager claim of thecoupon, the clearing-house-manager is configured to monitor the walletassigned to the store-manager. The system is configured to not publiclydisclose the discount key or the discount information. The store-manageris further configured to transfer, to a wallet associated with theclearing-house-manager, the coupon; and to detect the store-manager'sclaiming of the coupon, the clearing-house-manager is configured todetect the transfer, to a wallet associated with theclearing-house-manager, the coupon.

Implementations can provide an array of advantages, including thefollowing. By using encrypted data within blockchain-tracked coupon,discount information can be kept secret while the status of the couponcan be maintained in an open and reliable datastore. Use of a blockchainmanaged by many computers owned by users with an incentive to keep theblockchain operational can provide all users with reliability andsecurity without the overhead, cost, or problems that can arise with asingle administrator or point of failure. Encryption keys can bemaintained in private, ensuring that unauthorized observers are not ableto decrypt information about coupons that are redeemed in a publiclyaccessible blockchain. By use of a blockchain network, a clearing housecan credit a store immediately upon redemption of a coupon, or fasterthan other traditional coupon redemption schemes.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an example system for minting, redeeming,and crediting coupons with a blockchain.

FIG. 2 is a block diagram of example wallets that store coupons in ablockchain network.

FIG. 3 is a flowchart of an example process performed by a couponminter.

FIG. 4 is a flowchart of an example process performed by astore-manager.

FIG. 5 is a flowchart of an example process performed by aclearing-house-manager.

FIG. 6 is a schematic diagram that shows an example of a computingdevice and a mobile computing device.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

A blockchain network can be used to track coupons used when purchasinggoods. These coupons may be inspected by any computer in communicationwith the blockchain, but the use of encrypted data within the couponscan allow for the hiding of sensitive information like such as thediscount information within the coupon. For example, the blockchainnetwork can be configured so that coupons are locked with a hashlock andthe demonstration of a preimage that can be hashed into the hashlock isrequired for claiming the coupon. Further, the coupon's discountinformation can be encrypted with an encryption key, called a discountkey, that is required to unencrypt the discount information. Bycontrolling access to the preimage and the discount key, elements of theotherwise public coupon can be kept hidden from public observation.

FIG. 1 is a block diagram of an example system 100 for minting,redeeming, and crediting coupons with a blockchain. In the system 100are a coupon-minter 102, a customer computer 104, a store-manager 106,and a clearing-house-manager 108. Some or all of these computer systems102-108 can work together to operate a blockchain network 110 that isused to track a coupon 112 and other coupons.

The coupon-minter 102, customer computer 104, store-manager 106, andclearing-house-manager 108 are computer systems that are configured tostore and process data, to communicate with each other and othercomputing systems, and to perform other computing tasks. They mayinclude servers, desktop and laptop computers, mobile devices, andvirtual machines. The coupon-minter 102 can be used by an organizationthat receives a request from, for example, manufacturers to create anddistribute coupons for a particular product or product line. Thecoupon-minter 102 can create these coupons and distribute one suchcoupon 112 to a customer 104 in the blockchain network 110.

The customer computer 104 may include a home computer or mobile phoneowned or operated by a consumer that will use the coupon 112. Once thecustomer has the coupon 112 (or information about it), the customer mayuse the customer computer 104 when making a transaction at a store thatsells a product that is discounted by the coupon 112. When the customermakes this purchase, the store-manager 106 can claim the coupon 112 andprepare the coupon 112 for credit. The clearing-house-manager 108 candetect that the store-manager 106 has claimed the coupon, and credit thestore with the credit value of the coupon 112.

In order to accomplish some or all of these actions, some or all of thecomputer systems 102-108 can operate the blockchain network 110. Theblockchain network 110 can include a ledger that records transactionsthat are submitted to the blockchain network 110 and approved by thecomputer systems that operate the blockchain. In some configurations,for a submitted transaction to be approved, it must pass some form oftest or approval as determined by the constituent computing systems. Inthis example, coupons may be associated with a hashlock. In order for acoupon to be claimed, the claimer must provide a piece of informationcalled a preimage. The preimage is a data object that, when hashedaccording to a predetermined hash function, produces the hashlock.Because hash functions are one way—in at least practice if not always intheory—the only source for the preimage is from the party that createdthe hashlock. This party may then distribute the preimage to anotherparty in order to allow that other party to claim ownership of thecoupon 112 in the blockchain network 110.

These features may be used to allow for a controlled distribution of thecoupon 112. The coupon minter 102 can, on behalf of a manufacturer, mintmany coupons with discount information specified by the manufacturer.The coupon-minter 102 can, for each of these many coupons, createassociated unique preimages. From each of these many preimages, thecoupon-minter 102 can create many associated hashlocks. Then, the couponminter 102 can distribute, to customers, unique pairs of coupon IDs andpreimages. For example, coupon minter 102 can distribute the coupon IDand the preimage of the coupon 112 to the customer computer 104. Thisdistribution may be done, for example, by email, print flier, textmessages, or another distribution channel.

The customer may then produce the coupon ID and preimage when making apurchase of the item discounted by the coupon 112. The store-manager mayreceive the coupon ID and preimage and use these two pieces ofinformation to claim the coupon 112. As previously explained, the coupon112 has a hashlock that prevents claiming of the coupon 112 without thepreimage. By producing the preimage with the coupon ID, thestore-manager 106 has effectively demonstrated that they have beenauthorized to claim the coupon 112.

The clearing-house-manager 108 can detect the store-manger's 106claiming of the coupon 112 and can begin the process of crediting thestore from the manufacturer that commissioned the coupon. In order tocredit the store, the clearing-house 108 must be able to access thediscount information for the coupon 112. However, it is often desired bymanufacturers and others to keep discount information private fromparties not involved in the transactions of a particular coupon. Inorder to keep the discount information private, a discount key may beused to encrypt the discount information.

The coupon minter 102, when minting the coupon 112, can generate aunique encryption key called a discount key. This key may be used tosymmetrically encrypt the discount information for the coupon 112. Thatis, a single discount key may be used to both encrypt and decrypt thediscount information for a given coupon. When a coupon-minter 102creates a run of otherwise identical coupons, each of the coupon'sdiscount information may be encrypted with a different encryption key.This can result in the same discount information across many coupons,but with each coupon holding different encrypted data. In this way, itmay be made harder to guess what discount information is in a particularrun of coupons, especially if a run of coupons does not begin with thesame discount information in every coupon.

In some cases, additional information or personalized information may beadded to the discount information. For example, a nonce may be used tosalt the discount information so that otherwise identical discountinformation is not identical before encryption. In another example,information about the coupon, intended recipient, intended distributionchannel, etc. may be added to the discount information beforeencryption. This may provide, for example, less uniformity of thediscount information, which may increase the difficulty of analysis ofattacks on the encrypted discount information that attempt to learn ofthe discount information without access to the discount key.

In the example shown here, the coupon-minter 102 can provide to thecustomer computer 104 the discount key together with the coupon ID andpreimage as previously described. The customer computer 104 mayoptionally use the discount key to verify the discount information ifdesired by the user, but the system 100 can operate whether or not theuser-computer 104 decrypts the discount information.

When making a purchase, the customer computer 104 can produce thediscount key in addition to the coupon ID and the preimage. Thestore-manager 106 can use the discount key to decrypt the encrypteddiscount information and determine if the discount should apply to thecustomer's purchase. For example, the discount information may specify aproduct, an expiration date, contingent circumstances (e.g., only withpurchase of another product). If the store-manager 106 determines thatthis discount information should apply, the store-manager 106 can adjustthe customer's purchase accordingly. If the store-manager 106 determinesthat the discount information does not apply, and if the customer doesnot choose to alter their transaction to make it apply (e.g., purchasingthe discounted product instead of a mistakenly selected competitorproduct), the store-manager 106 can reject the coupon and discard thediscount key.

As part of claiming the coupon 112, the store-manager 106 may encryptthe discount key using a public key of the clearing-house-manger 108 andadd the encrypted discount key to the coupon 112. This public key may bepublished publicly by the clearing-house-manger 108 or another system,and may be the public half of a public/private key pair. Inpublic/private encryption schemes, anyone with the public key canencrypt information but only the holder of the private key can decryptthe information. Using this feature, the store-manager 106 has encryptedthe decryption key in a way that only the clearing-house-manager 108 candecrypt.

Upon detection of the store-manager's 106 claiming of the coupon 112,the clearing-house-manager 108 can decrypt the encrypted discount key,and then use the decrypted discount key to decrypt the discountinformation. Once gaining access to the discount information, theclearing-house-manager 108 can credit the store-manager 106 with thecredit value of the coupon 112 on behalf of the manufacturer. In thisway, the coupon 112 may be minted, transferred, and redeemed withoutpublicly disclosing the discount key or the discount information.

Alternatively, instead of monitoring for a store-manager 106 to claimthe coupon 112, the clearing-house-manager 108 can maintain a wallet ofits own and monitor that wallet for coupons. This may allow, forexample, a store-manager 106 to hold a number of coupons and redeem themin batch operations. This may result in, for example, lower overhead andadministrative costs, depending on the configuration of the system.Because the store-manager 106 is initiating a transfer out of their ownwallet instead of a party initiating a transfer into a wallet, theblockchain network 110 may not require a preimage for a hashlock tocomplete this transfer.

FIG. 2 is a block diagram of example wallets 200 and 202 that storecoupons in a blockchain network. In this example, a coupon 204represents a coupon as minted by a coupon-minter and before the coupon204 has been claimed by a store-manager. A coupon 206 represents asimilar coupon after it has been claimed by a store-manager.

The wallets 202 and 204 are data constructs that contain, in ablockchain network, a particular entity's digital goods. In the case ofa blockchain network that tracks at least coupons, the wallets 200 and202 can contain coupons like the coupons 204 and 206. The data to recorda data object in a wallet often takes the form of an entry in a ledgerthat records the minting of an object in a particular wallet (identifiedwith a wallet address), or the transfer of an existing data object froma source address to a destination address.

The coupon 204 can be created by a coupon-minter or held by a customer.The coupon 204 can include a hashlock, a coupon ID, and discountinformation that has been encrypted with a discount key. As previouslydescribed, the preimage and discount key may be needed to generate thehashlock and encrypted discount information, however the preimage anddiscount key themselves are not included in the coupon 204.

Claiming a coupon involves producing the preimage and transferring thecoupon to a wallet associated with the claimer. For example, if astore-manager claims the coupon 204, it is moved to the store's wallet202 from the source wallet 200 associated with the coupon-minter orcustomer. Claiming the coupon also can include modifying the coupon 204into the coupon 206. The discount key can be encrypted with a clearinghouse's public key and added to the coupon 206. In some implementations,this addition may be atomic with the claiming—that is, moving the couponto a different wallet may be performed as a single indivisible actionwith editing the coupon. In some implementations, claiming and modifyinga coupon may be divisible operations that may be performed separately.

FIG. 3 is a flowchart of an example process 300 performed by a couponminter. For example, the process 300 may be performed by thecoupon-minter 102. Therefore, the following example will be describedwith reference to the elements of the system 100. However, anothersystem or systems may be used to perform the process 300 or a similarprocess.

A coupon order is received 302. For example, a coupon serviceorganization may operate the coupon-minter 102 and theclearing-house-manager 108 as part of offering coupon services tomanufacturers and marketers. The coupon service organization may receivean order to generate a coupon campaign for a line of frozen burritosfrom a manufacturer and distributor of the burritos. The coupon-minter102 can receive an order for, for example, a particular number ofcoupons each offering a discount of one dollar off the purchase of theburritos to be distributed to customers that have expressed an interestin receiving coupons related to frozen foods and fitting some othercriteria.

Unique coupon IDs are created 304. To prepare to fill this order, thecoupon-minter 102 can generate or allocate a number of unique coupon IDsneeded to fulfill the order. For example, if the order was for threethousand coupons, the coupon-minter 102 can generate three thousandunique coupon IDs. Coupon IDs can be of types that allow unique anddifficult to guess values. These coupon IDs may be sequential integers,non-sequential random tokens in a name-space many orders of magnitudelarger than the token size (e.g., to make tracking and guessing by thirdparties harder), or universally unique identifiers (UUIDs). In somecases, the coupon IDs are used by the blockchain to index all coupons.In some cases, the coupon IDs may be different than an identifier usedby the blockchain to index coupons and/or different data objects.

Unique preimages and discount keys are generated 306. For each uniquecoupon ID, the coupon-minter 102 can generate a unique preimage and aunique discount key. The coupon-minter 102 can use a true-random orpseudo-random source to generate the preimage and discount keys. Thesize and format of the preimage and discount keys may be dependent onthe particular requirements of the security arrangement of the system100. For example, the system 100 may specify that the keys should have aparticular minimum size or conform to a particular format. This canresult in the coupon-minter 102 having a list of unique coupon IDs, witheach coupon ID having associated one unique preimage and one uniquediscount key.

Unique coupons are minted 308. For example, the coupon-minter 102 cangenerate discount information for the received order. This discountinformation can include a purchase discount that is to be applied when acustomer uses the coupon, a credit value that specifies the value of acredit that should be given to a merchant that receives the coupon, anexpiration date, terms and conditions, etc. Additionally, otherinformation such as a random nonce may be included. In some cases, theorder may specify a mix of different coupons (e.g., some for one dollaroff, some for two dollars off; some for one flavor and some for adifferent flavor), but in this example the order specifies that allcoupons should be the same one dollar off all flavors.

The coupon-minter 102 can then encrypt the discount information witheach unique discount key, resulting in unique encrypted discountinformation for each unique coupon ID. Because a third party would nothave access to the discount keys, the third party would not be able todetermine if any two examples of encrypted discount information containthe same unencrypted discount information.

The coupon-minter 102 can also hash each preimage into an associatedhashlock value by running each preimage through a one-way function. Forexample, the Secure Hash Algorithm 256 (SHA 256) or the Keccak 256algorithm could be used, to name only two possibilities.

With this information available, the coupon-minter 102 can mint thecoupons by, for example, combining each unique coupon ID with itsassociated hashlock and encrypted discount information. For example, thenewly-minted coupon may take the form of a string of alpha-numericcharacters resulting from the concatenation of the coupon ID, hashlock,and encrypted discount information; a structured data object in theExtensible Markup Language (xml) language; a JSON object; or printedonto piece of paper in a barcode such as a QR code.

Each new coupon is introduced 310 into a blockchain network. Forexample, the coupon-minter 102 may submit each coupon as a new entry inthe ledger of the blockchain network 110, specifying that the coupon beadded to a wallet associated with the coupon-minter 102. Computersystems that operate the blockchain network 110 may vote on theintroduction, and only add the coupon to the ledger if a sufficientnumber (e.g., simple majority or other threshold) approve thetransaction. These computer systems may check, for example, if theminter an authorized part of the blockchain network and/or if thetransaction is valid (e.g., formatted appropriately, within permissionscope, operating on a valid coupon ID).

Coupon IDs and keys are distributed 312 to customers. For example, thecoupon-minter 102 may maintain one or more distribution channelsseparate from the blockchain network 110 through which couponinformation may be transmitted to customers. In this example, somecoupon information is added to a template to generate coupon images thatcan be printed; and some coupon information is sent via email. However,any appropriate distribution channel for sending information may beused. This may include, but is not limited to, print (e.g., direct mail,circulars, coupon books, free-standing inserts), email, website andother internet destinations, and mobile or desktop applications.

In another configuration, the coupon-minter 102 may place couponsdirectly into wallets associated with customers. For example, thecustomer computer 104 may register with the coupon-minter 102 to show aninterest in receiving coupons. This registration may include identifyinga wallet associated with the customer computer 104. When thecoupon-minter 102 adds the coupon 112 to the blockchain network 110, thecoupon-minter 102 may specify that the coupon 112 should be placed inthe wallet of the customer computer 104.

FIG. 4 is a flowchart of an example process performed by astore-manager. For example, the process 400 may be performed by thestore-manager 106. Therefore, the following example will be describedwith reference to the elements of the system 100. However, anothersystem or systems may be used to perform the process 400 or a similarprocess.

A coupon ID and keys are received 402 from a customer. For example, acustomer can bring their customer computer 104 with them to the grocerystore. The customer can bring up an email received from thecoupon-minter 102 that contains a barcode containing a coupon ID,preimage, and discount key. A clerk at the store can scan this barcodeand verify that it does apply to the burritos that the customer ispurchasing.

The store-manager 106 may also use the scanned discount key to decryptthe discount information. In order to do so, the store-manger 106 mayread a copy of the encrypted discount information from the coupon 112from the blockchain network 110. The store-manager 106 then decrypts theencrypted discount information and verifies that the discountinformation specifies a dollar off the customer's purchase of the frozenburritos.

A coupon is claimed 404 from the blockchain network with the preimage.In response to a successful redemption of the coupon by the customer,the store-manager 106 can apply the one-dollar discount to the purchaseof the frozen burritos, and can claim the coupon from the blockchainnetwork 110.

To claim the coupon 112, the store-manager 106 can submit a claimrequest to the blockchain network 110. The claim request can include thecoupon ID and preimage as collected from the barcode. Computing systemsthat operate the blockchain network 100 can receive copies of this claimrequest and determine if it should be honored. For a claim request to bevalid, the preimage of the claim request must be of a value that, whenhashed, matches the hashlock. The computing system may verify thepreimage by hashing it and then voting to accept or reject the claimrequest depending upon the result of this comparison. In this example,the store-manager 106 received a valid coupon ID and preimage from thecustomer, and the claim request is accepted. As a result, the coupon 112moves from a wallet associated with the coupon-minter 102 to a walletassociated with the store-manager 106.

The discount key is encrypted 406 with a clearing house public key andthe coupon is updated 408 with the encrypted discount key. For example,the store-manager 106 may encrypt the discount information and submit amodification request to the blockchain network 110 to modify the coupon112 with the discount information encrypted with the clearing housepublic key.

In some implementations, the claiming 404 and updating 408 may beperformed as a single, atomic function. That is, the claiming andupdating may be requested, and may either succeed as a single functionor fail as a single function. By constraining the claiming 404 andupdating 408 to be atomic, the system may be able to avoid a state inwhich the claiming 404 succeeds but the updating 408 fails.

The above described interactions with the blockchain may be subject toapproval voting by the computer systems that manage the blockchain. Forexample, this voting may require a majority of such computing systems toexamine a request and vote to accept it if it appears to be a validrequest.

FIG. 5 is a flowchart of an example process performed by aclearing-house-manager. For example, the process 500 may be performed bythe clearing-house-manager 108. Therefore, the following example will bedescribed with reference to the elements of the system 100. However,another system or systems may be used to perform the process 500 or asimilar process.

Claiming of a coupon by a store-manager is observed 502. For example,the clearing-house-manager 108 can observe transactions in theblockchain network 110. When a transaction moves the coupon 112 from thecoupon-minter's 102 wallet to the store-manager's 106 wallet (or fromanother wallet such as the customer-computer's 104 wallet, or from awallet into the clearing-house-manager's 108 wallet), theclearing-house-manager 108 may identify this as a claim by thestore-manager 106

The encrypted discount key is decrypted 504 with a private key. Theclearing-house-manager may use a private key to decrypt the discountinformation that was encrypted by the store-manager 106 with thematching public key. By doing so, the clearing-house-manager 108 cangain access to the discount information.

A credit value is identified 506 from the discount information andcredit is applied 508 to the store's account. With the store identifiedand a credit value from the discount information identified, theclearing-house-manager 108 can credit the credit value to the store.This may take the form of, for example, a bank transfer, a check sent tothe store, or another appropriate form of payment. In some cases,credits may be aggregated to reduce transaction costs. For example, allcredits for a day or week may be aggregated into one payment at the endof that time window.

FIG. 6 is a schematic diagram that shows an example of a computingsystem 600. The computing system 600 can be used for some or all of theoperations described previously, according to some implementations. Thecomputing system 600 includes a processor 610, a memory 620, a storagedevice 630, and an input/output device 640. Each of the processor 610,the memory 620, the storage device 630, and the input/output device 640are interconnected using a system bus 650. The processor 610 is capableof processing instructions for execution within the computing system600. In some implementations, the processor 610 is a single-threadedprocessor. In some implementations, the processor 610 is amulti-threaded processor. The processor 610 is capable of processinginstructions stored in the memory 620 or on the storage device 630 todisplay graphical information for a user interface on the input/outputdevice 640.

The memory 620 stores information within the computing system 600. Insome implementations, the memory 620 is a computer-readable medium. Insome implementations, the memory 620 is a volatile memory unit. In someimplementations, the memory 620 is a non-volatile memory unit.

The storage device 630 is capable of providing mass storage for thecomputing system 600. In some implementations, the storage device 630 isa computer-readable medium. In various different implementations, thestorage device 630 may be a floppy disk device, a hard disk device, anoptical disk device, or a tape device.

The input/output device 640 provides input/output operations for thecomputing system 600. In some implementations, the input/output device640 includes a keyboard and/or pointing device. In some implementations,the input/output device 640 includes a display unit for displayinggraphical user interfaces.

Some features described can be implemented in digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The apparatus can be implemented in a computerprogram product tangibly embodied in an information carrier, e.g., in amachine-readable storage device, for execution by a programmableprocessor; and method steps can be performed by a programmable processorexecuting a program of instructions to perform functions of thedescribed implementations by operating on input data and generatingoutput. The described features can be implemented advantageously in oneor more computer programs that are executable on a programmable systemincluding at least one programmable processor coupled to receive dataand instructions from, and to transmit data and instructions to, a datastorage system, at least one input device, and at least one outputdevice. A computer program is a set of instructions that can be used,directly or indirectly, in a computer to perform a certain activity orbring about a certain result. A computer program can be written in anyform of programming language, including compiled or interpretedlanguages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment.

Suitable processors for the execution of a program of instructionsinclude, by way of example, both general and special purposemicroprocessors, and the sole processor or one of multiple processors ofany kind of computer. Generally, a processor will receive instructionsand data from a read-only memory or a random access memory or both. Theessential elements of a computer are a processor for executinginstructions and one or more memories for storing instructions and data.Generally, a computer will also include, or be operatively coupled tocommunicate with, one or more mass storage devices for storing datafiles; such devices include magnetic disks, such as internal hard disksand removable disks; magneto-optical disks; and optical disks. Storagedevices suitable for tangibly embodying computer program instructionsand data include all forms of non-volatile memory, including by way ofexample semiconductor memory devices, such as EPROM (erasableprogrammable read-only memory), EEPROM (electrically erasableprogrammable read-only memory), and flash memory devices; magnetic diskssuch as internal hard disks and removable disks; magneto-optical disks;and CD-ROM (compact disc read-only memory) and DVD-ROM (digitalversatile disc read-only memory) disks. The processor and the memory canbe supplemented by, or incorporated in, ASICs (application-specificintegrated circuits).

To provide for interaction with a user, some features can be implementedon a computer having a display device such as a CRT (cathode ray tube)or LCD (liquid crystal display) monitor for displaying information tothe user and a keyboard and a pointing device such as a mouse or atrackball by which the user can provide input to the computer.

Some features can be implemented in a computer system that includes aback-end component, such as a data server, or that includes a middlewarecomponent, such as an application server or an Internet server, or thatincludes a front-end component, such as a client computer having agraphical user interface or an Internet browser, or any combination ofthem. The components of the system can be connected by any form ormedium of digital data communication such as a communication network.Examples of communication networks include, e.g., a LAN (local areanetwork), a WAN (wide area network), and the computers and networksforming the Internet.

The computer system can include clients and servers. A client and serverare generally remote from each other and typically interact through anetwork, such as the described one. The relationship of client andserver arises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

What is claimed is:
 1. A system comprising: a coupon-minter configuredto perform operations including: generating a coupon comprisingencrypted discount information, wherein the encrypted discountinformation is encrypted with a discount key; generating, for thecoupon, a hashlock from a preimage; introducing the coupon to ablockchain in association with the hashlock, wherein the blockchain isconfigured to permit claiming of the generated coupon only uponreceiving access to the preimage used to generate the hashlock, whereinto introduce the coupon to the blockchain in association with thehashlock, the coupon-minter is configured to introduce the coupon to theblockchain in a wallet assigned to the coupon-minter; a store-managerconfigured to perform operations including: claiming, using thepreimage, the coupon in the blockchain; encrypting the discount key witha clearing-house public key; updating the coupon with the encrypteddiscount key; and a clearing-house-manager configured to performoperations comprising: detecting the store-manager's claiming of thecoupon; decrypting the encrypted discount key with a clearing-houseprivate key to re-generate the discount key; and decrypting theencrypted discount information with the discount key.
 2. The system ofclaim 1, wherein the coupon-minter, the store-manager, and theclearing-house-manager are each further configured to authenticaterecords of claims submitted to the blockchain.
 3. The system of claim 1,wherein: the coupon-minter is further configured to: receive an order togenerate a plurality of coupons, each having the discount information;and generate a plurality of coupons, including the coupon, each of theplurality of coupons having the discount information and each of theplurality of coupons having a different preimage.
 4. The system of claim1, wherein to claim the coupon in the blockchain, the store-manager isconfigured to move the coupon from the wallet assigned to thecoupon-minter to a wallet assigned to the store-manager.
 5. The systemof claim 4, wherein to observe the store-manager claim of the coupon,the clearing-house-manager is configured to monitor the wallet assignedto the store-manager.
 6. The system of claim 1, wherein the system isconfigured to not publicly disclose the discount key or the discountinformation.
 7. The system of claim 1, wherein the store-manager isfurther configured to transfer, to a wallet associated with theclearing-house-manager, the coupon; and to detect the store-manager'sclaiming of the coupon, the clearing-house-manager is configured todetect the transfer, to a wallet associated with theclearing-house-manager, the coupon.
 8. A method performed by dataprocessing apparatus, the method comprising: generating, by acoupon-minter, a coupon comprising encrypted discount information,wherein the encrypted discount information is encrypted with a discountkey; generating, by the coupon-minter, for the coupon, a hashlock from apreimage; introducing, by the coupon-minter, the coupon to a blockchainin association with the hashlock, wherein the blockchain is configuredto permit claiming of the generated coupon only upon receiving access tothe preimage used to generate the hashlock, wherein introducing thecoupon to a blockchain in association with the hashlock furthercomprises introducing the coupon to the blockchain in a wallet assignedto the coupon-minter; detecting, by a clearing-house-manager, astore-manager's claiming of the coupon; decrypting, by theclearing-house-manager, an encrypted discount key with a clearing-houseprivate key to re-generate the discount key; and decrypting, by theclearing-house-manager, the encrypted discount information with thediscount key.
 9. The method of claim 8, the method further comprising;claiming, by the store-manager, the coupon in the blockchain;encrypting, by the store-manager, the discount key with a clearing-housepublic key; and updating, by the store-manager, the coupon with theencrypted discount key.
 10. The method of claim 9, wherein thecoupon-minter, the store-manager, and the clearing-house-manager areeach further configured to authenticate records of claims submitted tothe blockchain.
 11. The method of claim 9, the method further comprises:receiving, by the coupon-minter, an order to generate a plurality ofcoupons, each having the discount information; and generating, by thecoupon-minter, a plurality of coupons, including the coupon, each of theplurality of coupons having the discount information and each of theplurality of coupons having a different preimage.
 12. The method ofclaim 8, wherein claiming the coupon in the blockchain comprises movingthe coupon from the wallet assigned to the coupon-minter to a walletassigned to the store-manager.
 13. The method of claim 12, wherein toobserve the store-manager claim of the coupon, theclearing-house-manager is configured to monitor the wallet assigned tothe store-manager.
 14. The method of claim 9, wherein the blockchain isconfigured to not publicly disclose the discount key or the discountinformation.
 15. The method of claim 9, the method further comprising:transferring, by the store-manager, the coupon to a wallet associatedwith the clearing-house-manager; wherein detecting the store-manager'sclaiming of the coupon comprises transferring, by theclearing-house-manager, the transfer, to a wallet associated with theclearing-house-manager, the coupon.
 16. A non-transitory computerstorage media encoded with computer program instructions that, whenexecuted by one or more processors, cause a computer device to performoperations comprising: generating, by a coupon-minter, a couponcomprising encrypted discount information, wherein the encrypteddiscount information is encrypted with a discount key; generating, bythe coupon-minter, for the coupon, a hashlock from a preimage;introducing, by the coupon-minter, the coupon to a blockchain inassociation with the hashlock, wherein the blockchain is configured topermit claiming of the generated coupon only upon receiving access tothe preimage used to generate the hashlock, wherein introducing thecoupon to a blockchain in association with the hashlock furthercomprises introducing the coupon to the blockchain in a wallet assignedto the coupon-minter; detecting, by a clearing-house-manager, astore-manager's claiming of the coupon; decrypting, by theclearing-house-manager, an encrypted discount key with a clearing-houseprivate key to re-generate the discount key; and decrypting, by theclearing-house-manager, the encrypted discount information with thediscount key.
 17. The computer storage media of claim 16, the operationsfurther comprising; claiming, by the store-manager, the coupon in theblockchain; encrypting, by the store-manager, the discount key with aclearing-house public key; and updating, by the store-manager, thecoupon with the encrypted discount key.
 18. The computer storage mediaof claim 17, wherein the coupon-minter, the store-manager, and theclearing-house-manager are each further configured to authenticaterecords of claims submitted to the blockchain.
 19. The computer storagemedia of claim 17, further comprises: receiving, by the coupon-minter,an order to generate a plurality of coupons, each having the discountinformation; and generating, by the coupon-minter, a plurality ofcoupons, including the coupon, each of the plurality of coupons havingthe discount information and each of the plurality of coupons having adifferent preimage.
 20. The computer storage media of claim 16, whereinclaiming the coupon in the blockchain comprises moving the coupon fromthe wallet assigned to the coupon-minter to a wallet assigned to thestore-manager.
 21. The computer storage media of claim 20, wherein toobserve the store-manager claim of the coupon, theclearing-house-manager is configured to monitor the wallet assigned tothe store-manager.
 22. The computer storage media of claim 17, whereinthe blockchain is configured to not publicly disclose the discount keyor the discount information.
 23. The computer storage media of claim 17,the operations further comprising: transferring, by the store-manager,the coupon to a wallet associated with the clearing-house-manager;wherein detecting the store-manager's claiming of the coupon comprisestransferring, by the clearing-house-manager, the transfer, to a walletassociated with the clearing-house-manager, the coupon.
 24. The systemof claim 1, the system further comprising one or more computing devicesconfigured to operate the blockchain such that the blockchain isconfigured to permit claiming of the generated coupon only uponreceiving access to the preimage used to generate the hashlock.
 25. Themethod of claim 8, the method further comprising operating theblockchain such that the blockchain is configured to permit claiming ofthe generated coupon only upon receiving access to the preimage used togenerate the hashlock.
 26. The computer storage media of claim 17, theoperations further comprising operating the blockchain such that theblockchain is configured to permit claiming of the generated coupon onlyupon receiving access to the preimage used to generate the hashlock.